Every man I know has a version of this list. The sauna after a workout. The cold plunge in the morning. The two cups of coffee before a meeting. The drink on Friday. Maybe a Zyn at the desk. Maybe a gummy on the weekend.

Most of those habits show up in the podcasts we listen to and the feeds we scroll through as part of a longevity or optimization routine. For general health, many of them have real evidence behind them.

For fertility, the answers are different. Sometimes very different.

I sat down with Brooke Boskovich for the Our TIES podcast and ran through the list. Brooke Boskovich is a functional medicine dietitian specializing in fertility and reproductive health. Over the past nine years, she has helped hundreds of couples overcome fertility challenges and finally take home healthy babies, even after years of trying. She combines evidence-based nutrition with a holistic, root-cause approach to identify and remove the barriers that stand in the way of optimal fertility. She was also one of our advisors on the TIES Foundations formulation.

Here's what she said, one item at a time.

Saunas

Brooke's answer: bad, during the preconception window.

This one surprised me. Saunas have well-documented health benefits for cardiovascular function, recovery, and longevity. For sperm, though, the mechanism runs the wrong direction.

"When we're talking about sperm, the male body is designed to keep sperm outside the body to keep them cool largely," Brooke said. "When we're heating up that body temperature and that scrotal temperature, it causes a lot of damage."

Cam asked her about the workaround she has seen online, such as putting an ice pack on during a sauna session. Brooke's take: your internal body temperature is still heating up. A cooling object on one spot doesn't change that.*

"If you want to do a personal experiment with that, do a semen analysis, and then wait three months while you sauna and see what happens," she said. "But I would say just to avoid it, preconception time."

Cold plunges

Brooke's answer: it depends.

Unlike saunas, cold plunges don't have a simple verdict. Brooke said there's real nuance around temperature, duration, and where a man's baseline fertility sits to begin with. Some men tolerate it fine. Some men see negative impacts if it's too extreme.

"It's hard for me to say absolutely not, or yes, it's fantastic, because of those factors that seem to be coming into play," she said.

Her recommendation was to go deeper on this one, and she mentioned she has a full episode on cold plunging on her own podcast for anyone who wants the detail.*

Caffeine

Brooke's answer: dose matters.

A cup of black coffee in the morning is typically fine. The issue with caffeine isn't caffeine itself; it's the stress response at high doses. Brooke explained that too much caffeine can elevate cortisol and create the kind of internal stress environment that works against fertility.

"But if we're talking about a cup of black coffee in the morning, that's typically totally fine," she said.

Alcohol

Brooke's answer: depends on what else is going on.

Brooke's guidance here was specifically linked to a marker called DNA fragmentation, which refers to breaks in the DNA inside sperm cells. If a man's DNA fragmentation is high, she recommends eliminating alcohol because alcohol is what she called "a negative offender" in that context.

If DNA fragmentation is low and the man is otherwise supporting his overall stress, nutrition, and sleep, "a drink or two a week supported by that can be okay."

The answer isn't zero for everyone. The answer is contextual.*

Marijuana

Brooke's answer: no.

This was her cleanest verdict in the whole conversation. No caveats, no dose nuance, no "depends."

"I don't recommend any THC products," she said.

When I asked her which of all the habits on our list she would flag as the most important to watch, THC was the one she singled out.

"Even a small amount of marijuana or THC is definitely impacting negative sperm parameters," she said. "And I see that in practice too."

She told us about a recent client who had stopped all other THC use but was drinking THC-infused beverages. Everything else in his lifestyle was dialed in. It wasn't until he stopped the drinks that his DNA fragmentation marker turned around.

"He was doing everything else as far as supporting fertility goes," she said. "So I would say that's a pretty strong offender."

Nicotine Pouches

Brooke's answer: not recommended.

"Even though it's not tobacco, the nicotine is a negative, definitely a big negative one," she said.

Nicotine is the issue, regardless of the delivery system. Zyn doesn't involve tobacco, but the active compound is the same one found in cigarettes, and for sperm, that's still a problem.

The takeaway

If a man is preparing for fatherhood, the list to watch isn't the same list as longevity or optimization. A sauna routine that supports a forty-year-old's recovery can work against a thirty-year-old's fertility. A gummy on the weekend that would raise no flags for general health can move a fertility marker.

The most important thing I took away from this part of the conversation with Brooke is that fertility demands a specific lens. The question to ask about any habit, before and during the preconception window, isn't just "is this good for me." It's "is this good for the specific thing my body is trying to do right now."*

We've got more conversations like this one coming. If you want them in your inbox, subscribe to the TIES newsletter. More real answers from real experts, built the hard way, on purpose.

*This post reflects conversations from the Our TIES podcast and is intended for general informational purposes only. It is not medical advice, a diagnosis, or a treatment recommendation, and it should not be used as a substitute for professional medical guidance. Always consult a qualified healthcare provider about any health condition, including questions related to fertility. Quotes from Brooke Boskovich have been lightly edited for readability. The meaning has not been changed.

Community notes

• DNA fragmentation refers to breaks in the DNA inside sperm cells. High fragmentation is associated with longer time to conception, higher miscarriage rates, and other outcomes. It is not typically part of a standard semen analysis and has to be ordered separately.

• Preconception window refers to the roughly three-month period before attempting to conceive, which corresponds to one full sperm production cycle. Lifestyle changes during this window have the most direct effect on the sperm that will eventually be involved in conception.

• Brooke's guidance on each of these lifestyle factors reflects her perspective from years of clinical practice working with couples on fertility. Individual responses vary based on baseline health, overall lifestyle, dose, and duration of exposure. The guidance here is directional, not personalized.

• Research on cold plunging specifically for male fertility is still limited; Brooke's nuance reflects that the evidence is mixed and depends on individual factors. For deeper detail on cold plunging, she has a full episode on her own podcast.

• The evidence base on THC and sperm parameters is growing and consistently points to negative effects on count, motility, morphology, and DNA fragmentation. Causal relationships and dose-response curves are still being studied, but Brooke's clinical observation aligns with the direction of the research.

• Nicotine's effects on sperm parameters are well documented regardless of delivery method (cigarettes, vapes, pouches). Research specifically on newer nicotine pouch products is less extensive than research on cigarettes, but the underlying mechanism is the same compound.

• This post covers six specific lifestyle factors Brooke addressed in the podcast. It is not a comprehensive list of everything that affects male fertility.